Stir Processing Research Articles

Influence of SiC Content on Microstructure and Tribological Properties of Friction Stir-Processed SiC/AA5083 Surface Composites

The present work aims to produce silicon carbide (SiC) particles-reinforced AA5083 surface composites through friction stir processing (FSP). The influence of SiC content on the microstructure and tribological properties of the friction stir-processed (FSPed) AA5083/SiC surface composites was investigated. The results reveal that the distribution of SiC particles within the stirred zone was homogeneous, irrespective of location, and SiC particle volume fraction. Good SiC/AA5083 interfacial bonding was obtained for all surface composites with refined grains. Electron backscattered diffraction results revealed that the stir zones comprised dynamically recrystallized, fine-grained, and equiaxed microstructures. Transmission electron microscopy revealed that dislocations rearranged to form high-angle grain boundaries upon dynamic recrystallization. The worn surface showed that an increase in SiC volume fraction transforms the wear from severe plowing, and delamination to light abrasive wear. The surface composites showed a substantial decrease in wear rate with an increase in SiC volume fraction due to the homogeneous distribution of SiC particles, grain refinement, and improved hardness. The wear debris of AA5083 alloy showed large flakes as a sign of severe plastic deformation whereas, surface composite samples comprised of fine wear debris.

The Quality Improvement of Molten Aluminium Alloy in Melting Process by Stirring Process and the Degassing Technique

The fuel-fired crucible furnace is very popular for melting of aluminium alloys. This melting technique provides good control of hydrogen gas in aluminium casting. The fuel type is LPG for convenience and low cost of production in small and medium foundry. However, the quality of the melt such as homogeneity of chemical composition is not good and stirring is normally required. In this paper, the rotary degassing system was used to improve the quality of the molten aluminium alloy. By control the homogeneity of chemical composition and reduces other impurities such as Iron (Fe). Two different inert gases, argon and nitrogen, were used to treat the melt. The combination of blade design, type of gas and rotation speed is the key success to improve the quality of molten aluminium alloy in this study. Moreover, this rotary degassing system can be used to control pouring temperature which is one of the most important parameters for the consistency of casting quality. Therefore, the rotary degassing system will be of benefit to control the homogeneity of chemical composition, control the pouring temperature, save production time and increase productivity of aluminium melting and casting.

Microstructure evolution and mechanical properties of friction stir welded FeCrNiCoMn high-entropy alloy

ABSTRACTTo investigate the microstructural development and mechanical properties of friction stir welded high-entropy alloy, the stirring process and the air cooling period were separated for discussion. The texture component developed from A* {111}<112> to A {111}<110> in the stirring stage, and finally changed to B {112}<110> in the subsequent air cooling stage caused by the multiple mechanisms including discontinuous dynamic recrystallization, continuous dynamic recrystallization, static recovery and selected grain growth. This work also demonstrated that the static recovery and the selected grain growth during the air cooling stage remarkably deteriorated the microstructure and mechanical properties which is produced during the stirring stage, and it cannot be neglected when investigating the microstructure transformation and mechanical properties during the friction stir welding.

Dynamic mechanical properties of enhanced filler dispersion polyethylene-glycol/q-SiO2 composites

In this work, polyethylene-glycol (PEG)/q-SiO2, (silica quartz) composites were prepared by dispersing q-SiO2, in various fractions, i.e., 0, 20, and 40 wt.%. We elaborated the silica dispersion in the polymer matrix from the previously reported solid method (reported in [1]) and a liquid method. In the latter, the dispersion of q-SiO2, in the matrix was done by a stirring process in the liquefied polyethylene glycol with temperature control. The filler content and mixing method were selected to optimize the dynamic mechanical properties of composites, especially, the shear moduli (G’ from the Dynamic Mechanical Analyzer (DMA) instrument. The maximum shear modulus value was found with 40 wt.% q-SiO2, by the liquid method, which showed 46% increment as compared to 40 wt.% q-SiO2, by the solid method. We showed in this work that the dynamic mechanical properties are tightly related with the dispersion of the filler in the matrix. The quantitative analysis of filler dispersion was done using PixelProfile software and dispersibility characterization from SEM-EdX images. We analyzed each image in three regions by RGB (Red-Green-Blue spectrum). The lower the dispersibility index (Idispersibility), the better the filler dispersion. By applying the liquid method, the dispersibility indices were 0.357 for 20 wt.% and 0.705 for 40 wt.%, better than solid method.

Optimization of wear behaviour using Taguchi and ANN of fabricated aluminium matrix nanocomposites by two-step stir casting

Among the composites, the metal matrix composites have involved considerable attention because they provide a wide range of properties and microstructures. Wear is one of the important phenomena that takes place in MMCs interface. The reinforcement enhances the performance of the matrix significantly. In this paper, A356/SiCn nanocomposites (AMNCs) are fabricated by two-step stir casting. The SiCn is mechanically alloyed with aluminum powder to improve their wettability in the AMNCs. SiCn is incorporated by changing weight percentage. The stirring process is employed to disperse SiCn in the molten matrix. Then the composites are poured into a metallic die. Microstructural study of the worn surface is performed by SEM. Taguchi and ANN are used to optimize and analyze the controlling factors. Based on the current study, it is found that reinforcement is the most influencing factor followed by the load which affects the wear loss. ANN results show better predictability with an R-squared value of 99.23% than Taguchi approach with an R-squared value of even 81.99%. Hence, ANN is also used to explore the behavior of each factor. The percentage contribution of SiCn is the highest (60.15%) followed by sliding distance (35.33%). SEM analysis reveals that the presence of SiCn and oxide layers are the responsible factors for increasing wear resistance. Further the present work can significantly provide a guide to save time using Taguchi and ANN for wear test and for the industrial preparation of AMNCs with a uniform reinforcement distribution by two-step stir casting.

An Evaluation of the Water Quality Characteristics of Shipboard Sewage Disposal and Usability Based on Water Quality Enhancement

International Maritime Organization recognizes vessel-induced pollution as a global issue. The designation of the Baltic Sea as the special uncontaminated area was the beginning of the regulations for preventing marine pollution. In this regard, a process is needed which meets the provisions of MEPC. 227(64) for the specificity and constrained conditions of vessels, removes both nitrogen and phosphorus, requires convenient operation and low construction cost and is little affected by the load variation of inflow. This study used an SBR(sequencing batch reactor) and MBR(membrane bioreactor) combined process to iterate the stirring and aeration process and maintained the ratio of raw wastewater parameters (C:N:P) to be 10:3:1 in order to assess the quality and future availability of ultimate outflow in each time period of the stirring and aeration process. The removal efficiencies of COD and T-N exceeded 90% and 93% respectively. However, a detailed mechanism will be identified by a further study on nitrogen removal issues like DO aeration condition, stirring duration, ORP and NO3. As the removal efficiency of T-P exceeded 95%, the SBR and MBR process formed anaerobic and aerobic conditions without a separate coagulation process for removing phosphorus, thereby enabling easy phosphorus release and uptake. The optimal stirring and aeration condition seems to be 70–50 min. A further study will be efficiently conducted by focusing on the water quality criteria of the Maritime Environment Protect Committee. 227 (64) for E. coli and chlorine and a detailed mechanism.

Characterization of curd grain size and shape by 2-dimensional image analysis during the cheesemaking process in artisanal sheep dairies

The size and shape of curd grains are the most important parameters used by cheesemakers to decide when to end the cutting or stirring processes during cheesemaking. Thus, 2-dimensional image analysis was used to measure the characteristics of curd grains in commercial cheese productions carried out by artisanal sheep dairies. Dairies used different technical settings for cutting and stirring steps, causing differences in the size and shape of curd grains. A linear relationship between total revolutions used for cutting and stirring and curd particle size was established. However, particle size distributions after curd cutting and stirring were highly heterogeneous. Actual cheese yield was correlated with particle size and cutting revolutions, whereas curd grain shape and fat loss were associated with stirring conditions by a multivariate approach. Image analysis of the size and shape of curd grains gives useful information for determining characteristics related to cheese yield and quality and may contribute to improving and controlling the cheesemaking process in small artisanal dairies.

Investigation of mechanical behavior of dissimilar material FSBR joints exposed to a marine environment

The focus of this research is the mechanical behavior of dissimilar material friction stir blind riveted (FSBR) joints after a 6-month exposure to a marine environment with two different material configurations, i.e., CFRP (carbon fiber-reinforced plastic) composite/Al and Mg/CFRP composite. Quasi-static tensile tests along with fractographic and acoustic emission (AE) analyses were employed to explore the effect of corrosion on the mechanical behavior of each individual constituent material and the entire joints. All the exposed constituent materials showed significant degradation in terms of maximum load and nominal stiffness, along with the change in failure mode for the exposed joints. However, the exposed joints exhibited similar strengths as the as-fabricated ones, where the fracture area of all joints was localized at the joining region between the rivet and workpiece (tension failure mode). The joint strengths were similar because of the metallurgical bonding and mechanical interlocking (occurred during the stirring process) which consequently eliminated the gap and prevented the corrosion at the bonding interface between the rivet and workpieces. This observation revealed FSBR as a promising joining technology for the dissimilar material joining applications in corrosion prone environments. In addition, compared to the as-fabricated joints, more AE hit signals were observed during the tension test for the exposed joints due to the fracture of introduced brittle corrosion products.

PROCESSING MCHINE, REFRIGERATOR AND MILK PACKAGING SYSTEM WITH 3-IN-1 INTEGRATED PROCESS

The purpose The purpose of this study is to provide solutions to problems that exist in SMEs Cow Milk Momoo, especially the problem of production processes that the process is still using the traditional way and the tool is still relatively simple. Method The method used is to utilize Temperature Controller on Processing Machine, cooling, and packing Cow Milk that serves to regulate the cooking temperature so that the heat generated can be more evenly distributed. Processing, refrigeration and packing machines Cow Milk is also equipped with a Wiper Motor instead of stirring which is still manual so that the stirring process can run automatically. In addition to this machine also uses Heat Exchangers technology soaked in water so as to be able to overcome the problem of cooling process is still simple. Results The expected result is the increased productivity and efficiency of the production process so that the productivity of SMEs of Cow Milk Momoo can increase 2-fold which initially yields an average of 150 liters of Cow Milk / day can produce up to 300 liters of Cow Milk / day. The Findings The findings of this research are the use of Temperature Controller, Wiper Motor, and Heat Exchanger as solution of SMEs Cow Milk Production Process Problem. Keywords: Cow Milk, ,SMEs, Temperature Controller, Heat Exchanger,Wiper Motor

Argon Bubble Coalescence and Breakup in a Steel Ladle with Bottom Plugs

Gas‐stirred ladles are widely used in the steel secondary refining process. In order to produce high‐quality steel, a range of stirring conditions, from hard stirring for mixing to gentle stirring for inclusion removal, is required. In this paper, a full scale unsteady three‐dimensional computational fluid dynamics (CFD) model is developed to simulate the bubble behavior in a steel ladle. A volume of fluid (VOF)‐Lagrangian approach is applied to simulate multiphase flow characteristics. The VOF method is used to track the liquid steel and slag, while the Lagrangian method is used to track the movement of argon bubbles. A water model is used to validate the gas‐stirred ladle model against experimental data. Flow field and bubble breakup and coalescence phenomena inside the ladle is studied in the baseline case, and the effects of initial bubble diameter and gas flow rate during the stirring process have been investigated through parametric study as well.

APLIKASI PROSES TEMPERING UNTUK OPTIMASI TITIK LELEH COKELAT HITAM PRODUK PENGOLAHAN PINTAS

This research is to study the effect of tempering conditions on the change of melting point of dark chocolate produced through a stage of heating and cooling with the stirring process at low-speed. Melting point, hardness, and stickiness were measured in the combination of three different tempering conditions: low temperature (29°C, 31°C, and 33°C), high temperature (45°C, 47.5°C, and 50°C), and tempering time (10 minutes, 17.5 minutes, and 25 minutes). Optimum tempering conditions were evaluated using Response Surface Method (RSM). The best tempering condition was obtained at the combination of low temperature at 31°C, high temperature at 47.5°C, and tempering time at 17.5 minutes. This combination resulted melting point, hardness, and stickiness at 36.5°C, 746.3 g, and -89.941 g respectively. Thus, attainment of optimum tempering condition was central to the desired properties of produce which melt at human body temperature with the minimum level of hardness at room temperature . The best chocolate product is easily melted at human body temperature, but it is hard at room temperature and also have a minimum adhesiveness cause. Keywords : chocolate, hardness, melting point, r esponse s urface m ethod , tempering

Effect of travelling magnetic field inductor characteristics on the liquid metal flow in a rectangular cell

Contactless liquid metal stirring by traveling magnetic field (TMF) inductor is widely applied in modern metallurgy. The quality of stirring is an actual challenge. One solution to this problem is to complicate the TMF inductor supplying current form. In present work we study the influence of the current on the hydrodynamic characteristics of the flow. The spatial distribution of the velocity field is investigated. The goal is to reduce stagnation zones in the flow and to achieve uniform stirring. Local turbulence characteristics, which has a significant effect on the stirring process, are also investigated. In this case, the purpose is to generate the flow with a sufficient intensity of the turbulence. The research is carried out by mathematical simulation and experiments. Three-dimensional calculations are performed in the Comsol Multyphysics software. The experiment is carried out on gallium eutectic. The total electromagnetic force dependencies on the supplying current characteristics are obtained taking into account the magnetic saturation. Three-dimensional flow calculations are verified on the experimental data. The flow characteristics on the TMF inductor supplying current value are determined.

Physical Simulation of Solid Liquid Mixture Stability in Molten Aluminum

Mixing behaviour is a very important process for preparation of aluminum foam by foaming in melt route due to the dispersion of foaming agent, thickening agent or stabilizing agent being added into the liquid metal. However, some unfavourable factors, such as active chemical properties, easy oxidation and evaporation, no fixed shape and opacification of liquid metal at high temperature, result in it is very difficult to observe the melt stirring and changing process. The mixing behaviour of molten aluminium matrix composite was simulated on the basis of water-based system. In addition to visual observation of the mixing effect, gray histogram was introduced to analyse the dispersion of solid particles in aqueous solution quantificationally. The whole experimental procedures were recorded by MV-Capture industrial camera and the intercepted image information was converted to digital information, i.e. standard deviation originated from the gray histogram. The results showed that the stabilization of aqueous solution can be characterized by the obtained digital information and the physical simulation can provide guidance for the fabrication of metal foams.

A Prototype Downdraft Gasifier Design with Mechanical Stirrer for Rice Straw Gasification and Comparative Performance Evaluation for Two Different Airflow Paths

In this research, a prototype downdraft throatless gasifier was designed with a mechanical stirrer. The gasifier was designed for gasification of rice straw pellets. The diameter of the reactor was 350 mm and a nominal value for the heat power of biomass input was 70 kW. Rice straws which were collected from Thrace Region of Turkey gasified for determination of the designed gasifier performance in Namik Kemal University Biosystem Engineering Laboratories. The effects of airflow path and stirring process on the gasification efficiency during the gasification process were investigated. Temperatures and airflow rates observed and adjusted by controlling the air flow rate in the automation system constantly. Pellets were gasified using two different airflow paths with the same equivalence ratio of 0.2 and these were compared. Air inlet from the top showed better results than air inlet from tuyeres. For the air inlet from the top, the higher heating value of producer gas was determined as 5.047 MJ Nm-3 and cold gas efficiency was calculated as 65.4%. H2/CO ratio was found as 1.385 which was higher than the air inlet from tuyeres.

Cold model study of sound signals from gas-stirred ladles

ABSTRACTThe stirring power required achieving uniform composition and temperature in ladle metallurgy is a function of the volumetric gas flow rate, metal depth, and slag thickness. Accurate estimation of the stirring power requires the precise determination of the amount of metal and slag depth. The present study found that frequencies of the acoustic signal generated during the stirring process can indicate the depths of metal depth as well as slag thickness. This is promising as it offers a potentially simple technique for simultaneously detecting slag thickness and stirring in ladles.

PEMBERIAN WORKPLACE STRETCHING EXERCISE DAN MODIFIKASI KONDISI KERJA DAPAT MENURUNKAN KELUHAN MUSKULOSKLETAL DAN KELELAHAN PADA PEKERJA PEMBUAT DODOL TRADISIONAL DI DESA TAMBLANG – KABUPATEN BULELENG

The activity of traditional dodol stirrer workers is done with standing position. The stirring process is done monotonically and over a long period of 5 hours. This study aims to show that workplace stretching exercise administration and modification of working conditions may decrease musculoskeletal and fatigue complaintas in traditional dodol stirrer workers. The stirring tool (siut) used by the worker does not correspond to anthropomethry, causing a work with a bent position.&#x0D; This study was an experimental study, with the same subject design. Period I subjects were treated with conventional working condition. Period II subjects were treated with workplace stretching exercise administration and improved working conditions in the form of re-design the stirring tool(siut) of the dodol stirrer and active rest. Musculoskeletal complaints were measured by Nordic body map questionnaires on a 4 likert scale, working fatigue using 30 item rating scales.&#x0D; Analysis of the collected data is started with the descriptive analysis and the normality data tested using Shapiro-Wilk. Further, the data that has normal distribution are analyzed using t-paired and the data that has not a normal distribution are analyzed using Wilcoxon test. This study indicated that the administration of workplace stretching exercise and modification of working conditions can decreasing musculoskeletal decline of 18.3 % from the mean 12.67±0.50 to 5.59±0.52 and fatigue decreased by 18.5% from the mean 12.42±1.45 to 5.34±0.66&#x0D; It can be concluded that the provision of workplace stretching exercise and modification of working condition can decrease musculoskeletal complaintas and fatigue of dodol stirrer workers. So it is advisable for the dodol making industry to applied this technique of exercise to minimize complaints due to the working process of stirring dodol.

Improved strengthening efficiency of nanoreinforcements realized by a novel melt spinning process

Abstract

Calcium precursor from stirring processes at room temperature for controllable preparation of nano-structure CaO sorbents for high-temperature CO2 adsorption

Nano-structure CaO crystals with an average size of 480 nm × 255 nm (length and width) were prepared by simply roasting CaCO3 precursors at 900 °C for 2 h. The CaCO3 precursors with a pure vaterite crystalline phase were readily synthesized by a room temperature stirring method using Ca(NO3)2 and CO2 storage material (CO2SM). The CO2SM played an important role in providing CO32− source and structure controlling. The effects of CO2SM dosage, Ca2+ concentration, and stirring time on the crystallization of CaCO3 precursors were investigated. In addition, the CO2SM was successfully regenerated by simply exposing the filtrate from the preparation process to CO2 for further preparing CaCO3 precursor. The as-obtained CaO crystals exhibited a strong CO2 adsorption capacity up to 17.18 mmol g-1 under 0.1 MPa at 700 °C.

Ultra-grain refinement and enhanced low-temperature superplasticity in a friction stir-processed Ti-6Al-4V alloy

An ultrafine microstructure consisting of α grains (~ 0.51 µm) and a small amount of β phase was successfully achieved in a friction stir-processed (FSPed) Ti-6Al-4V alloy. The fraction of high angle grain boundaries (HAGBs) with random crystallographic orientations reached 89.3% revealed that dynamic recrystallization was responsible for the ultra-grain refinement mechanism during friction stir processing (FSP). Low-temperature superplasticity (LTSP) of such an ultrafine microstructure was demonstrated in the temperature range of 550–650 °C and strain rates of 1 × 10−4–3 × 10−3 s−1. Specifically, an extremely superior LTSP of 1130% was achieved at 600 °C and 3 × 10−4 s−1, which was explained by means of the ultrafine equiaxed grains, a large proportion of HAGBs with random orientations as well as the presence of β phase. The predominant superplastic deformation mechanism was considered as grain boundary sliding associated with grain boundary diffusion.

Obtaining Ultra-High Surface Area TiO&lt;sub&gt;2&lt;/sub&gt; Nanorods via Hydrothermally Transformation of Elongated Titanate Nanotubes

In this paper, a tunable TiO2nanorod cross-link structure with ultra-high surface area (up to 109.81 m2/g) has been successfully prepared via hydrothermally treating elongated sodium titanate nanotubes. XRD, SEM, HRTEM and BET analysis were employed to characterize the morphology and inner structure of the samples. The preparation conditions (the hydrothermal temperatures and the pH values of the solutions) of the obtained TiO2products were systematically studied. The maximum length of nanorod reaches to 1 μm while the lateral size could be limited less than 10 nm. The surface area can be easily tuned by modifying the stirring rate during the hydrothermal process. In addition, the photocatalytic performance of synthesized TiO2nanorods were also measured, and the nanorod structure with ultra-high surface area showed much better photocatalytic activity than the sample produced without stirring process, which can be attributed to the influence of the large difference in specific surface area of the obtained TiO2products.